Scarlet Witch is a major character in Uncanny Avengers at the moment, it's Quicksilver that's not being used much. IF they wanted to change the twins status in the comics, which I highly doubt, then the Inhumanity event would be a good place to do it. Supposedley, the Terrigan Mists are unleashed on Earth and begin affecting people, so that COULD be the way to make them Inhumans. I don't think it will happen, but there's always a chance.